In a chain saw, the saw chain runs on a guide bar which is mounted on the chassis or power head of the chain saw. The guide bar is a flat, elongated bar which projects forwardly from the chain saw power head and has a rounded forward end which may, if desired, comprise a roller or sprocket. The guide bar has spaced peripherally extending side flanges which define between them a peripherally extending groove. The saw chain is a link chain customarily comprising side links having surfaces which slide on the outer edges of the peripheral side flanges of the guide bar and center links which are provided with tangs which extend into the peripheral groove of the bar. These tangs guide the chain on the guide bar and are engaged by a sprocket adjacent the inner end of the guide bar in order to drive the chain.
By reason of the sliding friction of the chain on the guide bar, it is necessary to lubricate the chain in order to prevent heating and rapid and excessive wear. For this purpose it is known to provide the guide bar with an oil hole extending through one of the side flanges of the guide bar near its inner end. On the chain saw power head there is provided an oil tank or chamber connected by suitable passageways to the oil hole in the guide bar. A manually or power operated pump is provided for delivering the lubricating oil from the oil tank or chamber to the oil hole of the guide bar. The oil passing through the hole is picked up by the tangs of the chain running in the groove of the guide bar and distributed around the guide bar so as to lubricate the surfaces on which the chain runs. Lubrication of the guide bar and chain is thus provided